As this kind of air belt system, this applicant has disclosed an air belt system comprising an inflatable air belt, a gas generator for supplying gas into the air belt, the air belt including a pouched belt folded into the shape of a band and a cover for enclosing the pouched belt, wherein the cover can hardly stretch in the direction of the length, but can stretch in the direction of inflation of the air belt, and the stretch of the air belt in the direction of inflation shortens the longitudinal length of the air belt. (Japanese Patent Application No. 9-236903. Hereinafter referred to as the prior application.)
Referring now to drawings, the air belt system of the prior application will be illustrated. FIG. 1a is a perspective view of the interior of an automotive vehicle provided with the air belt of the prior application. FIG. 2a is a plan view of an shoulder belt and an lap belt illustrating near the coupled portion thereof. FIG. 2b is a plan view of a pouched belt; FIGS. 2c, 2d, and 2e are cross sectional views taken along lines C—C, D—D, and E—E of FIG. 2a respectively. FIG. 3a is a plan view of a shoulder belt with the air belt inflated, FIG. 3b is a plan view of a pouched belt in the state of being inflated, and FIGS. 3c and 3d are cross sectional views taken along lines C—C and D—D of FIG. 3a, respectively. FIG. 4 shows how to knit the air belt cover.
The air belt system 1 comprises a shoulder belt 2 extending diagonally across the passenger from the right side to the left side thereof, a lap belt 3 extending from the right side to the left side of the passenger, a buckle unit 4 disposed on the floor of the vehicle body or the like, a tongue 5 for being inserted into and engaged with the buckle unit 4 when the belt is to be fastened, and an intermediate guide 6 for guiding the shoulder belt 2.
The shoulder belt 2 is composed of a webbing 2A made of a normal belt which is of the same material as that for generally used conventional seat belts and an air belt 2B connected to one end of the webbing 2A. The webbing 2A is slidably drawn through the intermediate guide 6. The other end of the webbing 2A is coupled to a seat belt retractor (ELR) having a collision lock feature fixed to the vehicle body. The seat belt retractor 7 is adapted to wind up the webbing 2A.
The air belt 2B is so located as to be in contact with the passenger, and a tongue 5 is secured to the end thereof opposite the webbing 2A.
The lap belt 3 is made of a normal webbing which is of the same material as generally used a seat belt and coupled to the tongue 5 on one end and to a seat belt retractor (ELR) 8 fixed to the vehicle body on the other end. The buckle unit 4 further includes a gas generator 9 coupled thereto, which actuates and generates high pressure gas in case of emergency such as collisions.
The tongue 5 and the buckle unit 4 are provided with passages for allowing gas to pass from the gas generator 9 to the air belt 2B.
As shown in FIG. 2 and FIG. 3, the air belt 2B comprises an inflatable belt 10 and a tubular knit cover 12 enclosing the belt 10. The belt 10 is so shaped that the part coming on the chest and belly of the seated passenger is wider, and the wider part is to be folded into an elongated belt. Numeral 11 represents seams of the belt 10.
The knit cover 12 is flexibly expandable widthwise but can hardly stretch in the direction of the length. FIGS. 4a and 4b illustrate how to knit this knit cover, respectively.
FIG. 4a shows a normal warp knitted fabric comprising a knitting yarn 20, wherein a plurality of knitting yarns 20 (20A-20D) constitute loops R. Each loop is arranged in a staggered format to the right and left from top to bottom of the drawing. The tip portion of each loop R (for example, the tip portion of the loop RB2) is placed around the base of the adjacent loop (for example, the base of the loop RA1), and around the base thereof, the tip portion of the adjacent loop (for example, the tip of the loop RA3) is placed. Therefore, the loops R are arranged successively in row from top to bottom of the drawing, and loops made of the yarn coming from the right side and the loops made of the yarn coming from the left side are arranged alternately from top to bottom in one row; they are arranged from the top in the order of RA1, RB2, RA3, and so on.
FIG. 4b illustrates the fabric strengthened by adding additional yarns 30 to the knitting yarns 20, which thereby can be made thinner. The additional yarn 30 is inserted along a series of loops arranged from top to bottom passing through the intersections of the knitting yarns 20 alternately from the front to the back and again from the back to the front, and so on.
The air belt 2B and the lap belt 3 are both coupled to the tongue. The knit cover 12 is so constructed as to undergo the tensile load exerted to the air belt by being coupled to the webbing 2A and the tongue 5.
When the gas generator 9 is actuated in the state that the tongue 5 is engaged with the buckle unit 4, the air belt inflates. In this case, the length of the knit cover 12 along the length of the air belt 2B will be shortened, so that the air belt 2B will be brought into intimate contact with the passenger to ensure the significant protection of the passenger.
FIG. 5 shows the state that the knit cover 12 of warp knitted fabric using additional yarns as shown in FIG. 4b shortens in its longitudinal length when the air belt 2B (pouched belt 10) is inflated. As described above, the knit cover 12 can hardly stretch in the direction of the length of the belt due to the application of heat drawing processing. When the pouched belt 10 is inflated, the knitted loops of the knit cover 12 expand in the direction of the width, and as a result, the knit cover 12 contracts in the direction of the length, and therefore the longitudinal length of the air belt 2B will be shortened.
In the present air belt unit, when the gas generator actuates and the air belt is inflated, the cover expands as well. Since the cover can hardly stretch in the direction of the length of the air belt, the length thereof will be shortened when the air belt is inflated. Consequently, the length of the air belt will also be shortened so that the air belt is well fitted to the passenger to ensure the protection of the same.
The knit cover of the air belt system of aforementioned prior application requires specific stretching characteristics such that it can hardly stretch in the direction of the length of the air belt, but can stretch in the direction of the expansion of the air belt and thereby be shortened in length in the direction of the length of the air belt when the air belt is inflated, as well as a sufficient strength and superior comfortableness.